The present disclosure relates to a method for determining whether or not ground contact loss is imminent for a wheel of a vehicle. Moreover, the present disclosure relates to a computer program, a computer readable medium, a control unit for a vehicle and/or a vehicle.
The present disclosure can be applied in heavy-duty vehicles, such as trucks, buses and construction equipment. Although the invention will be described with respect to an articulated hauler, the invention is not restricted to this particular vehicle, but may also be used in other vehicles, for instance other types of work machines such as a wheel loader, a dumper truck, or any other type of construction equipment.
A vehicle, for instance a work machine, generally comprises a plurality of wheels that are adapted to propel and/or brake the vehicle. In order to ensure that the operation of the vehicle is conducted in a desired manner, it may be desired to have information as regards the condition of one or more of the plurality of wheels.
For instance, it may be desired to receive information as regards whether or not ground contact loss is imminent for one or tore wheels of the vehicle. In the event that it is determined that ground contact loss is imminent, there is for instance a risk for wheel slip and a modification of the operation of the wheels may be desired.
For instance, in the event that the several wheels are driving a vehicle and it is determined that ground contact loss is imminent for one or more of the wheels, a driving torque may be distributed from the ground contact losing wheels to the wheels that are determined to maintain ground contact. Purely by way of example, the above transfer may be executed by means of one or more differentials.
As another example, in the event that the several wheels are braking a vehicle and it is determined that ground contact loss is imminent for one or more of the wheels, a braking torque may be redistributed from the around contact losing wheels to the wheels that are determined to maintain ground contact.
US 2007/0179699 A1 discloses a method for determining whether or not wheel slip is imminent for a vehicle wheel. The method proposed in US 2007/0179699 A1 detects the lateral acceleration of the vehicle, compares the lateral acceleration thus determined with a predetermined amount of lateral acceleration, and uses the result of that comparison for determining whether or not an electronic differential should be activated.
However, it would be desired to obtain more robust method for determining whether or not ground contact loss is imminent for a wheel.
It is desirable to provide a method for determining whether or not ground contact loss is imminent for a wheel of a vehicle, which method is straightforward to use.
As such, the present disclosure relates to a method for determining whether or not ground contact loss is imminent for a wheel of a vehicle. The vehicle comprises a vehicle body having a vertical extension in a vertical direction. The wheel is allowed to be subjected to a relative vertical displacement, in the vertical direction, in relation to the vehicle body. The vehicle further is such that a maximum value of a vertical displacement of the wheel relative to the vehicle body is limited to a relative vertical displacement limit.
The method comprises:
determining an actual relative vertical displacement of the wheel relative to the vehicle body,
determining a limit margin as the difference between the actual relative vertical displacement and the relative vertical position limit and
determining that ground contact loss is in imminent for a wheel if the limit margin is within a predetermined vertical threshold range.
The above discussed method implies that it is possible to determine whether or not ground contact loss is imminent for a wheel of a vehicle without having to analyze complex data, such as estimates of the speed or slip of the wheel and/or accelerations of the vehicle. Instead, the risk that contact loss is imminent may instead be determined on the basis of measure data that are simple to estimate and determine, e.g. an actual relative vertical displacement.
Optionally, the vehicle comprises a bogie system. The bogie system comprises a plurality of wheels and the bogie system is such that each one of the wheels is allowed to be subjected to a relative vertical displacement in relation to the vehicle body. Optionally, the bogie system comprises a bogie beam connecting the wheels. The bogie beam is pivotable in relation to the vehicle body. The method may comprise determining a pivot angle of the bogie beam in relation to the vehicle body and using the pivot angle as a value indicative of the actual relative vertical displacement.
Measuring the pivot angle is a straightforward way of determining the actual relative vertical displacement of one or more wheels arranged on a bogie beam.
A second aspect of the present disclosure relates to a method for controlling the operation of a wheel of a vehicle.
The method comprises:
determining whether or not ground contact loss is imminent for the wheel using the method according to the first aspect of the present disclosure,
determining that ground contact loss is imminent and
reducing the torque that is transmitted to the wheel.
A third aspect of the present disclosure relates to a computer program comprising program code means for performing the steps of any one of the methods of the first and/or second aspect of the present disclosure when the program is run on a computer.
A fourth aspect of the present disclosure relates to a computer readable medium carrying a computer program comprising program code means for performing the steps of any one of the methods of the first and/or second aspect of the present disclosure when the program product is run on a computer.
A fifth aspect of the present disclosure relates to a control unit for a vehicle. The control unit is adapted to determine whether or not ground contact loss is imminent for a wheel of the vehicle. The vehicle comprises a vehicle body having a vertical extension in a vertical direction. The wheel is allowed to be subjected to a relative vertical displacement, in the vertical direction, in relation to the vehicle body. The vehicle further is such that a maximum value of a vertical displacement of the wheel relative to the vehicle body Is limited to a relative vertical displacement limit.
The control unit is adapted to:
determine an actual relative vertical displacement of the wheel relative to the vehicle body,
determine a limit margin as the difference between the actual relative vertical displacement and the relative vertical position limit and
determine that ground contact loss is imminent for a wheel if the limit margin is within a predetermined vertical threshold range.
Optionally, the control unit is adapted to:
determine whether or not ground contact loss is imminent for the wheel using any one of the above discussed options,
determine that ground contact loss is imminent and
reduce the torque that is transmitted to the wheel.
A sixth aspect of the present disclosure relates to a vehicle, preferably a work machine, comprising a computer program according to the third aspect of the present disclosure and/or a computer readable medium according to the fourth aspect of the present disclosure and/or a control unit according to the fifth aspect of the present disclosure.
Further advantages and advantageous features of the invention are disclosed in the following description and in the dependent claims.